Tuberculosis remains the leading single cause of death from infection around the world; new treatments are needed to change the shape of the epidemic. One proposed approach to expanding the available arsenal of anti-TB drugs is targeting host factors to either enhance bacterial sterilization or modulate inflammation that drives tissue damage. Tissue damage in the context of infection is typically conceptualized on a linear spectrum, with ?too much? driving host-mediated tissue destruction and ?too little? resulting in progression of bacterial infection. However, this linear model fails to capture the complexity of inflammation in TB; in fact, some individual components of inflammation, including tissue remodeling enzymes such as matrix metalloproteases (MMPs), likely contribute to destruction without promoting sterilization. Inhibiting such enzymes could improve outcomes without compromising bacterial killing. We propose to take a systematic approach to identifying and targeting the matrix enzymes that contribute to tissue destruction in TB infection with two overarching goals: detailing the role of individual enzymes in TB pathogenesis and developing and testing highly specific inhibitors of those enzymes as adjunct host-directed therapies in TB treatment. In preliminary work using a murine model of cavitary TB, we performed serial transcriptional profiling of infected lungs to identify the destructive matrix enzymes upregulated during infection. MT1-MMP stood out as upregulated in an early and sustained pattern; this enzyme has previously been associated with human TB. Using a highly specific MT1-MMP inhibitor developed by the Sagi laboratory, we performed a pilot experiment to determine tolerability of low-level dosing over the first 8 weeks post-infection in the murine cavitary model of TB. Mice tolerated the inhibitor well, and although the inhibitor was not dosed for maximum efficacy, histopathologic analysis demonstrated a trend toward decreased lesion size and fewer dense inflammatory cell infiltrates. In this proposed work, we will build upon those results to test both a role for MT1-MMP in pathogenesis in this model and the effect of inhibition on molecular, cellular, and histologic outcomes of disease. In aim 1, we will optimize dosing to maximize inhibition without inducing side-effects; we will then test the effect of MT1-MMP inhibition on bacterial growth and lung histopathology. In aim 2, we will use single-cell transcriptional profiling to both identify cellular drivers of MT1-MMP production and test the impact of MT1- MMP inhibition on inflammatory cell recruitment to the infected lung. We will then test the impact of MT1-MMP inhibition on the inflammatory milieu using multiplexed cytokine profiling and high resolution microscopy. Upon achieving these aims, we anticipate having characterized the role of MT1-MMP in the pathologic progression of TB in a murine model of disease. We anticipate these results will inform targeted studies of the role of matrix enzymes in the pathogenesis of human TB; further, we anticipate these results will ultimately inform the development of MMP inhibitors as adjunctive therapies for TB.